Method and device for providing correlation means in hybrid telecommunication networks

ABSTRACT

Combinational networks provide simultaneous connectivity via networks of different network type between user equipment. For communication sessions on different network types, belonging to the same user equipment, a correlation check is enabled by introduction of an identifier denoted as Combinational Call Indicator (CCI). This CCI identifier in combination with the known Calling Line Identity (CLI) identifier enables user equipment and other and network entities to perform a correlation check between ongoing, or to be established, CScalls and PS-sessions. A user equipment, setting up a related communication session, sets the CCI identifier and provides the CCI identifier during the communication session setup towards the receiving user equipment or network entity, which is enabled to check whether the last received communication session is correlated to the earlier established session due to the presence of the CCI identifier.

This application claims the benefit of U.S. Provisional Application No.60/592.491, filed Jul. 30, 2004, the disclosure of which is fullyincorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates generally to telecommunications systems,such as fixed, wireless or hybrid communication networks, having apacket- and circuit switched architecture denoted as combinationalnetworks. More particularly, the present invention facilitates a methodfor relating two or more communication sessions, present or beingestablished in the packet- and circuit switched parts of said networksin an efficient way.

BACKGROUND OF THE INVENTION

Fixed- and especially mobile- networks, such as Global System for Mobilecommunications (GSM), General Packet Radio System (GPRS) or UniversalMobile Telecommunication System (UMTS) are constantly evolving. GSM/GPRSand UMTS networks today offer both Circuit Switched (CS) connectivityand Packet Switched (PS) connectivity. The PS end-to-end connectivitywith its capabilities for transmission of a wide range of data types maybe used for offering multimedia services such as image, music and videotransfer. The CS connectivity provides a reliable link between two UserEquipment by means of one or more trusted network-nodes with a reliableand defined Quality of Service (QoS).

Combinational networks, where two or more links of different type to oneor more User Equipment are established, are capable to deploy both CS-and PS-connectivity to a user equipment, thereby enabling services whichperform their activity by PS-communication sessions, denoted asPS-sessions and CS-communication sessions, denoted as CS-calls.

As to benefit from this form of service combination, user equipment arerequired that are capable of handling a CS-call and a PS-sessionsimultaneously. Multi Radio Access Bearer (RAB) terminals for UMTS andDual Transfer Mode (DTM) terminals for GSM/GPRS networks will beavailable; these types of terminals provide support for simultaneous CS-and PS-connectivity.

Today, conversational voice cannot be delivered over PS bearers to theend user, due to e.g. insufficient capacity in the Radio Access Networksin operation and therefore existing CS bearers are used for deliveringconversational voice. In the future, it may be possible that a single PSbearer is used for conversational voice and multimedia. Nevertheless,DTM terminals today, and possibly UMTS user equipment in the future,will deliver support for simultaneous CS- and PS-connectivity.

In order to give the end-user the look and feel of a single service,although the service may be composed of various CS- and PS-domainservices, deployed in the CS-network and the PS-network respectively, itis desirable to determine and deploy some form of relation betweenongoing CS-calls or CS-calls that are to be established and the ongoingor to be established PS-session(s).

Some examples of said desired to be determined relation:

-   1) It should be possible to provide the user of a DTM phone with a    rich alert, i.e. as opposed to a simple audio-only alert, as common    at a CS-call, the user gets a visual rendering as well. This visual    rendering could contain e.g. a photograph of the calling party, the    calling party's name or the priority of the call. As far as the    receiving party is concerned, it does not matter whether the CS-call    was made from a user equipment with PS capabilities or just a    “normal” (capable of CS-calls only) phone. In the latter case, an    entity in the network, e.g. an Internet protocol Multimedia    Subsystem (IMS) may have generated the “rich” part of the call. In    this case the alert at the receiving phone, initialised by a    CS-network, is related to the visual rendering at the receiving    phone-   2) To ease user interaction, it should be possible for parties    involved in a CS-call to be able to specify with ease (e.g. with a    single click of a button) that a picture, video or file shall be    sent to the party with which a speech communication is ongoing    (i.e., the current CS-call partner). In this case the ongoing    CS-call is related to the existing or new PS-session required for    sending said data portion.-   3) If a CS-call is established between users A and B, it would be    desirable to have the possibility to charge the PS-session (e.g.    exchange photos, share whiteboard, etc.) between the users A and B    with a different tariff than normal (i.e. as opposed to the tariff    that applies to the PS-session in isolation), and present the user a    single bill. In this case the charging of the PS-sessions is related    to the charging of the CS-call as to present said user a single    bill, which is traditionally related to CS-calls only.-   4) During an ongoing CS-call to a helpdesk or an assistance service,    it would be desirable for the helpdesk to have the possibility to    send additional multimedia (pictures/video with text) that    illustrates a solution to a problem. In this case the ongoing    CS-call is related to a PS-sessions where the additional multimedia    information is exchanged.-   5) It would be desirable to influence a QoS of a PS-session when a    CS-call is ongoing. For instance video streaming during the CS-call,    comprising a voice call, is handled with a higher priority. Here it    is required that the relation between the CS-call and the PS-session    has to be known by the user equipment, the network, or by both, as    to influence the QoS.

In all these examples stated above, it is desirable to determine arelation between the CS-call and the PS-session in such a way, that therelation is made known in a simple and reliable way without anyremarkable delay towards the user equipment or the network. Furthermoreit should be ensured towards the user that any costs generated for thePS-session are billed in a trusted way in relation to his/hers CS-call.

The problem that the invention seeks a solution to, is formulated as atwo-part problem.

A first part of the problem deals with: “How to find the relationbetween the CS-call and the PS-session?” More specifically, how can aservice determine whether or not a latest service trigger belongs to anongoing service? This needs to be resolved under differentcircumstances, namely: the latest service trigger concerns a CS- or aPS-service, the ongoing service itself is a CS- or a PS-service, andfinally the service may be resident in the user equipment or in thenetwork. This first part of the problem is defined as how to providecorrelation means for correlating the CS-call with the PS-session.

A second part of the problem deals with “How to provide an incentive tostart a process for finding the relation between the CS-call and thePS-session?” More specifically, how should an entity indicate, orsuggest, or point-out that the CS- and PS-services are correlated? Thissecond part of the problem is defined as how to induce a correlationbetween a CS-call and a PS-session.

Furthermore it should be desirable that the correlation induction takesplace at the communication means of the user or by an interceptingservice. Any solution to said problem must fulfill the followingrequirements:

-   -   The correlation between the CS-call and the PS-session should        not place extra requirements on the user, i.e. the user should        be able to spontaneously place the CS-call or start-up the        PS-session, not knowing whether he/she would initiate another,        related CS- or PS-service later during that call or session.    -   Any solution found should work on various networks, even if a        mix of various networks is deployed with different protocols.        This is applicable when a call crosses a Gateway node between        two networks, especially when these two networks are        heterogeneous, e.g. GSM & TDM or GSM & PSTN/ISDN etc.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a method ofinitialising and enabling correlation of communication sessions presentin a combinational network comprising networks of different type being aCS-network and at least one PS-network, where said communicationsessions being a CS-call at the CS-network and a PS-session at thePS-network are related to a party having a user equipment deploying saidsessions at said different types of networks.

It is a further object of the present invention to provide a userequipment which is arranged for performing said establishment of thecorrelation between said sessions by means of the method provided.

These objects are achieved by the method as claimed where depending onthe type of network (CS or PS) a communication session is setup wherebyone or two identifiers are provided to the other party's user equipment.

During a setup of a communication session on a CS-network, aCombinational Call Indicator (CCI) identifier is provided to the otherparty as to indicate that the communication session might be correlatedto an established or to be established communication session on aPS-network between the same parties. In case the setup of thecommunication session is executed on a PS-network, a Calling LineIdentification (CLI) identifier and the CCI are sent to the other partyas to indicate that the communication session on the PS-network might becorrelated to a communication session on a CS-network between the sameparties. The order in which the communication sessions are setup isirrelevant. Even simultaneous setup sessions are allowed.

The method claimed thus provides, with the presence of the CCIidentifier, means to detect that a communication session is related withanother communication session, and the CCI identifier provides as wellan incentive, to verify if the correlation between the communicationsessions is present. The order in which the communication sessions aresetup is irrelevant for the application of the invention. Evensimultaneously setup communication sessions are allowed.

The method according to the present invention is based on the insightthat two users, or a user and a network entity, are having simultaneouscommunication sessions to each other in a combinational network via e.g.a CS- and a PS-network, wherein the communication sessions are regarded“isolated” from each other in that the communication sessions couldexist without any reference to each other, even while being related toeach other from the user's perspective. In case communication sessionssuch as a CS-call at the CS-network and one or more PS-sessions at thePS-network should be related from the network point of view, thereshould exist a correlation between said communication sessions.

The following phases are be identified when attempting to correlate aCS-call and a PS-session:

-   -   (1) Establishing that correlation needs to be induced;        -   this decision is taken by one of the users' user equipment            or by the network.    -   (2) Generating references to indicate correlation, and        subsequently indicate, append or attach the said reference to a        respective CS-call or PS-session bearer, to facilitate        subsequent detection of correlation.    -   (3) Detecting that correlation detection is required.    -   (4) Executing the required correlation.

The last step of executing the correlation is context dependent and itsactual implementation depends on the network type and protocols deployedand is be deployed by known methods.

For the purpose of correlation of the CS-call and the PS-session thefollowing cases are distinguished:

a) a CS-call is ongoing and a PS-session is set up;

b) a PS-session is ongoing and a CS-call is set up;

-   -   c) a CS-call and a PS-session are set up simultaneously. For all        cases listed above, the correlation can either be induced in the        user equipment of the calling A-party or called B-party, or in        the network. While, the correlation needs to be detected in the        called or calling party's user equipment and/or in the network.

A first part of a solution to the problem stated above is to use anexisting identifier, namely a “Calling Line Identity” (CLI) identifierfor the purposes of correlation. The CLI is used in ISDN User Part(ISUP), contained in the Calling Party Number (CgPN), as to identify theuser or entity that creates a CS-call. The CLI is included in a CS-callestablishment process. As a second part of the solution a newidentifier, a “Combinational Call Indicator” (CCI) is created, whichshould be at least a one-bit variable (i.e. a flag), to indicate thatthe CS-call is part of a potential- or established-combinational callcomprising both a CS-call and a PS-session.

Regarding case a above) : in case the CS-call between an A-party and aB-party is ongoing and the PS-session with the B-party is set up by theA-party, a message from the A-party, comprising A-party's CLI and a“set” CCI identifier, is sent towards the B-party's user equipment viathe PS-network. On receiving the message with the CCI identifier byB-party's user equipment, B-party's user equipment determines from thepresence of the CCI identifier, that the ongoing CS-call is correlatedwith the incoming PS-session.

Regarding case b); in case a PS-session is ongoing between an A-partyand a B-party, and the CS-call by the A-party is set up, a “set” CCIidentifier is transferred together with a CS-call alert towards theB-party. As during set-up of the PS-session the CLI of the A-party'suser equipment has already been signalled to the B-party's userequipment, the B-party's user equipment determines from the presence ofthe CCI identifier that the ongoing PS-session is correlated with theincoming CS-call.

Regarding case c); in case the CS-call and the PS-session are set upsimultaneously by an A-party, a “set” CCI identifier is initialised bythe A-party at both the CS-call and the PS-session A message from theA-party, comprising A-party's CLI and a “set” CCI identifier, is senttowards the B-party's user equipment via the PS-network. Simultaneouslya CS-call by the A-party is set up and a “set” CCI identifier istransferred together with a CS-call alert towards the B-party. TheCS-call alert and the PS-session setup may be received in arbitraryorder at the B-party's user equipment. The CCI identifier, received bythe B-party's user equipment in either the CS-call alert or thePS-session setup, indicates that a combinational session is to beexpected, where the already received CS-call or PS-session is hencecorrelated with an expected PS-session or CS-call respectively.

An Internet Protocol Multimedia Subsystem (IMS) application at the userequipment provides the “setting” of the CCI identifier in the CS-callsetup and provides the “set” CCI Identifier and the CLI in a message forestablishing the PS-session.

As during the setup of the PS-session and the CS-call the CCI identifieris “set” for both communication sessions, and the CLI of the A-party'suser equipment is messaged to the B-party's user equipment on both theCS-network and PS-network as well, the B-party's user equipmentdetermines from the presence of the CCI identifier, that thecommunication session that arrived first is correlated with the nextincoming communication session.

The CCI identifier is inserted in the PS-network as well as CS-networksignalling. Other properties of the CCI identifier are that it is“writable” (induce-able) by the sending/receiving user equipment of theA-party or B-party as well as by the network, while it is “readable”(detectable) by the network and the sending/receiving user equipment.Furthermore, the network has the capability to delete/modify the CCIidentifier from the CS-call or PS-session bearer.

Messages exchanged between said users to establish communication and/orduring communication can be intercepted and modified by a “ServiceNetwork” comprising network entities having connections to networks ofdifferent network types within the combinational network.

The method of the invention as presented provides the user equipment,network entity or the service network, means to establish a correlationbetween communication sessions at a combinational network comprisingdifferent types of networks, where the said communication sessions aredeployed by the user equipment having communication sessions at networksof different type. By deploying the CCI identifier, the correlationestablishment is induced at the user equipment or the network, whereinthe CLI identifier enables the correlation between the communicationsessions. By means of this correlation method, as a set of examples,“rich” alerts is provided with a simple user interaction, chargingtariff adaptations of the PS-sessions are reliably deployed, multimediastreams could be simply correlated to the ongoing CS-call and the QoS ofthe PS-session could be influenced based on the establishment of thecorrelation with the CS-call.

These and other advantages according to the present invention are nowillustrated in more detail with reference to the enclosed drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 presents a schematic diagram of a combinational network with twouser equipment connected to the network.

FIG. 2 presents a schematic diagram of a user equipment

FIG. 3 presents a schematic diagram of a correlation node

DETAILED DESCRIPTION

Without restrictions to the scope of the invention, in order to providea thorough understanding of the present invention, the invention ispresented against the background and within the scope of the currentimplementation of a mobile communication system deployed in acombinational network environment. However, the present invention may bedeployed in any communication system comprising combinational networks.

Suppose that two users, A-party and B-party have communication sessionsongoing. Said communication sessions between the A-party and the B-partyconsists of a CS-call provided by a CS-network and a PS-session providedby a PS-network, both communication sessions regarded as “communicationcomponents”. The said components may be set up one after the other, inan arbitrary order, or simultaneously. User Equipment used by theA-party and the B-party shall allow for CS- and PS-communicationssessions simultaneously, which is referred to as dual-modecommunication. The said dual mode capability may be present in a singledevice or in a multitude of devices, such as a split user equipmentarrangement where said dual mode user equipment comprises e.g. a mobilephone and a Personal Computer (PC).

Messages exchanged between said users to establish communication and/orduring communication can be intercepted and modified by a “ServiceNetwork” comprising network entities having connections to networks ofdifferent network types within the combinational network.

FIG. 1 illustrates schematically a combinational network 10 comprisingseveral networks of different network type 11, 12, 13, with a first userequipment 1 and a second user equipment 2 connected to all or some ofthe networks 11, 12, 13. As to provide physical connection to thenetworks 11, 12, 13, the user equipment 1, 2 has network interfaces 1A,1B, 1C, 2A, 2B, 2C, each associated with a network address, towards saidnetworks 11, 12, 13.

For the explanation of the invention, it is arbitrary assumed thatnetwork 11 is a network of a CS-network type, and networks 12 and 13 areof a PS-network type.

The A-party may with his/hers first user equipment have a combinationalcommunication session with the B-party by means of user equipment 2, asis explained in the examples below. However the A-party mayalternatively have a combinational communication session with a networkservice node 34 comprised in the combinational network.

In the description below, it will be explained how a correlation of theCS-call with the PS-session will be established by the user equipment 1,2, followed by an explanation where the correlation will be establishedby the network 10, implemented as a network based correlation node 5having connections to networks of different type 11, 12, 13 comprised bythe combinational network 10.

The following cases are distinguished, for the purpose of correlation ofa CS-call and a PS-session:

-   -   a) CS-call is ongoing and a PS-session is set up;    -   b) PS-session is ongoing and a CS-call is set up;    -   c) CS-call and PS-session are set up simultaneously.

For all cases listed above it will be regarded that the inclusion of aCLI identifier in the CS-call establishment at the CS-network 11 isprior art.

For case a) the invention will be explained by means of a practicalscenario with reference to FIG. 1.

An A-party having the user equipment 1, such as a telephone, calls aB-party having the user equipment 2 by selecting B-party's phone numberfrom an address book in the telephone 1, or by “dialing” B-party'stelephone number.

A connection according to prior art will be established by means of theCS-type network 11. At a later instant, the A-party wants to sendpictures to the B-party.

For the A-party to experience the foregoing as a single service, theA-party should be required to do no more than just pressing one buttonto indicate “send the picture to my current CS-call partner”.

In response to the click, the A-party's user equipment 1 fetches thePS-network address 2B, 2C, of B-party's user equipment 2, which can bean Internet Protocol (IP) address, a Session Initiation Protocol (SIP)Universal Resource Identifier (URI) or presence URI [RFC 3859—CommonProfile for Presence (CPP), The Internet Society (2004)].

The PS-network address of the called B-party's user equipment 2, isknown to the A-party's user equipment. In the case that the A-partywould retrieve the PS-network address, a PS-address retrieval method isprovided by a method disclosed at co-pending application U.S.application Ser. No. 60/592,427. This co-pending application shows amethod and device for retrieving the PS address of the combinationalcall partner, where a retrieval for a PS-network address is initialisedby means of a CS protocol over a CS-network. The address retrievalrequest is being directed to the call partner or a network node thataccomplishes the network address request.

When the PS-network address is known to the A-party's user equipment, anexchange of terminal capabilities could be performed

If the A-party initiates the picture transmission and presuming a chargeof the CS-call and the PS-session (i.e. sending the pictures) shouldappear on one bill, then the combinational network 10 should be able todetermine that the CS-call and the PS-session belong to a singleservice. In other words, if the CS-call and the PS-session can becorrelated, the CS-call and the PS-session are related and form part ofa combinational communication session.

For enabling a correlation check the invention provides for the use ofidentifiers. A first identifier is an existing identifier, namely a“Calling Line Identity” (CLI) identifier for the purposes ofcorrelation. The CLI is used in ISDN User Part (ISUP), contained in theCalling Party Number (CgPN), as to identify the user or entity thatcreates a CS-call. The CLI is included in a CS-call establishmentprocess.

For correlation induction the invention provides a second identifier,being a “Combinational Call Indicator” (CCI) identifier, which should beat least a one-bit variable (i.e. a flag), to indicate that the CS-callis part of a potential- or established-combinational call comprisingboth a CS-call and a PS-session.

As to provide means for correlation between the ongoing CS-call by meansof the CS-network 11 and a PS-session which is to be established overthe PS-network 12, 13, a protocol is used to address B-party's userequipment 2. A suitable protocol would be Session Initiation Protocol(SIP). A SIP INVITE message is sent to B-party's user equipment 2 as toinitiate an Internet Protocol (IP) multimedia session, which carries theCalling Line Identification (CLI) of the A-party. Associating A-party'sCLI with the SIP INVITE is accomplished in a number of ways.

A logical place to include CLI is the “Call-ID” header in the SIP INVITEmessage. The Call-ID can be set to equal the CLI in E.164 format (referto International Telecommunication Union ITU-T Recommendation E.164[4]). Alternatively, the CLI can be just a part of the composition ofthe Call-ID, and extra information such as a timestamp can beappended/prepended in a recognisable format. The latter alternative hasseveral advantages in that the A-party is not limited to setting up aPS-session only with the CS-call partner; e.g. the A-Party sets upPS-sessions to another end-point.

Another option to include the CLI is in the “From” header of the SIPINVITE message. The CLI (essentially a telephone number) can beformatted as a telephony Universal Resource Identifier (URI) e.g. sip:+31161245656@kpn.nl and used in the “From” header in accordance withIETF RFC 2806 [1]. The “From tag” in the “From” header of the SIP INVITEmessage is used to create uniqueness.

A further option is to use the message body of the SIP INVITE toindicate the CLI. Time stamping, in addition to the CLI, can be used asa simple means to create uniqueness between SIP INVITE messagesoriginating from the same user equipment.

In all situations outlined above, the CCI identifier is also indicated(over and above the CLI), e.g. by means of a prefix or a suffix to theSIP INVITE message.

On receiving the message with the CCI identifier, via the PS-sessionover the PS-network 12, by B-party's user equipment 2, B-party's userequipment 2 determines from the presence of the CCI identifier, that theongoing CS-call is combinational when the CLI of the CS-call and the CLIretrieved from the PS-session are the same.

On receiving the CCI identifier, the receiving User Equipment or networkentity may initiate a procedure to check for a correlation between thecommunication sessions. A method for carrying out this actual check fordetermining that the CS-call and the PS-session are correlated, isdisclosed at co-pending application U.S. application Ser. No.60/592,426. This co-pending application shows a method where a number oflogical databases is introduced which contain actual data on relationsbetween network addresses and communication sessions, where acorrelation check is deployed by a correlation node. The check consistsof a number of queries towards said databases or to other networkentities, yielding whether the communication session is to be regardedas combinational.

Optionally, it could be the case that the B-party's user equipment 2 mayhave some settings that require that a correlation is detected in theB-party's user equipment 2, as e.g. it could be that the B-party is onlywilling to accept PS-sessions from CS-call partners.

This case, remarked as a spontaneous behaviour of the end-users of userequipment 1, 2, implies that the CS-call need not necessarily containthe CCI identifier at the time of call establishment.

Even if the CCI identifier is carried in the CS-call (when no PS-sessionexists), any user equipment 1, 2 involved or a network node 34 mustperform the combinational check, before correlation is established.Since there is no PS-session ongoing when only a CS-call is ongoing, thecombinational check will yield a negative result.

For case b) the invention will be explained by means of a practicalscenario with reference to FIG. 1. An A-party having the user equipment1 and a B-party having user the equipment 2 have a chat session (IPmultimedia service) ongoing. Due to delays incurred in the chat session,the A-party decides that it is better to have a full-duplex speechconversation while leaving the chat session ongoing, which he/she fallsback to when the critical points are discussed in the conversation.

The solution for the present case b) (CS-call set up after PS-session)is very similar to the solution for the case a), (PS-session set upafter CS-call). While the PS-session is set up, the identifiers CLI andCCI are carried in a SIP INVITE message in exactly the same way. Theonly difference is that the identifiers are carried in anticipation thatthe associated CS-call (requiring correlation) might be set up later.So, the CLI is still carried in the SIP INVITE message in the variousways described at case a).

The difference is how CCI identifier is carried. Once again, note thatsince the PS-session was set up first, the CCI identifier need not becarried in the SIP INVITE message that sets up the PS-session. But theCCI identifier can be carried in the CS-call.

As is specified above in the present invention, it is assumed that theCS-call uses DTAP, ISUP and DSS1 as bearer. Other bearer types can beused.

As during the set-up of the PS-session the CLI of the A-party's userequipment 1 has already been signalled to the B-party's user equipment2, the B-party's user equipment 2 is able to determine that the ongoingPS-session is combinational and hence correlated with the incomingCS-call, as the CCI identifier is “set”. Please see case a) for areferences to disclosure of a method for carrying out the actual checkfor determining that the CS-call and the PS-session are combinational.

Usually, charging for costs of a call is not trusted when the chargingprocess is established by terminals or user equipment 1, 2, thereforecharging is conventionally arranged by the network. When a combinationalcall is charged e.g. that a reduction of costs of a CS-call is achievedwhen a simultaneous CS-call and a PS-session are present between anA-party and a B-party's user equipment 1, 2, a network entity verifieswhether the CCI identifier is “set” rightly based on the actual presenceof said sessions. In case the CCI identifier is invalidly “set”, thenetwork entity modifies or disregards the current status of the CCIidentifier and does not apply the reduction of costs as presented at theexample above.

For case c) the invention will be explained by means of a practicalscenario with reference to FIG. 1. An A-party, having user equipment 1initiates a CS-call to a B-party having user equipment 2 and wants toinduce a “rich alert” into the B-party's user equipment 2. This isaccomplished by setting up a PS-session simultaneously with the CS-call.An IP Multimedia Subsystem (IMS) application in the A-party's userequipment 1 includes the CCI identifier in the CS-call establishment andincludes the CLI identifier in the PS-session establishment.

When the B-party's user equipment 2 receives the CS-call, the userequipment 2 deduces from the presence of the CCI identifier that itshall wait for the corresponding PS-session. When the PS-sessionarrives, the presence of the CLI in the PS-session indicates that thatPS-session is associated with the CS-call indicated by the CLI. TheB-party's user equipment 2 now offers the CS-call and PS-sessionsimultaneously to the B-party's user equipment 2. The CS-call and thePS-session form an “enriched alert”.

A further example of this case:

The A-party from the example above establishes a CS-call to theB-party's user equipment 2. The network 11, 12, 13, intercepts theCS-call establishment and induces a CCI identifier in the signalling.Simultaneously, the network establishes a PS-session to the B-party'suser equipment 2 and includes the CLI from the A-party in the PS-sessionsignalling.

As a result, the B-party's user equipment 2 receives an enriched alert,similarly to the previous example. In the present example, however, thenetwork generates the enrichment of the alert, as opposed to the callingparty's user equipment 1.

The implementation of “the network that induces the CCI identifier” isimplemented by a correlation node 5, having connections to the networks11, 12, 13 comprised by the combinational network 10. The correlationnode 5 comprises interfaces 5A, 5B and 5C each with an associatednetwork address, towards the networks 11, 12 and 13.

In all the three cases a), b), c) above, the correlation can either beinduced in the user equipment 1, 2 of the calling A-party or calledB-party or network service node 34, or in the network implemented ascorrelation node 5. While, the correlation needs to be detected in thecalled or calling party's user equipment 1, 2 or network service node 34and/or in the network based correlation node 5.

When correlation of a CS-call and a PS-session needs to be performed bythe network, as implemented by correlation node 5, this network node 5has means to detect the presence of the CCI identifier in the signallingprotocol. In an example embodiment of the present invention, the networknode 5 includes an Application Server (AS). The protocol that the ASuses to control the CS-call establishment requires suitable informationelements to carry the User-to-User Information (UUI) elements, which inturn contain the CCI identifier.

In addition, said control protocol would require a suitable informationelement to induce, modify or delete the User-to-User Information (UUI),which includes the CCI identifier. Protocols ISUP, DTAP and DSS1 providepossibility to exchange info in UUI elements.

An example of such protocol would be CAMEL Application Part (CAP) (see3GPP TS 29.078 [6]), which would need to be enhanced to contain the UUIin some of the CAP operations.

When a user equipment 1, 2 in a wireless telecommunication network 11,12, 13, such as a Mobile Station 1, 2 establishes a Mobile Originatedcall, it uses User-to-User Information (UUI) elements in the callestablishment messages. Refer to 3GPP TS 23.087 [5]. A UUI element iscarried over DTAP (from MS to MSC or MSC Server), over ISUP (betweenexchanges) and over DSS1 (towards a digital subscriber). The signallingnetwork provides for transparent transport of the UUI elements betweencalling and called party.

UUI elements are used to carry the CCI identifier. The signallingprotocols (ISUP, DTAP, DSS1) allow for the use of a UUI element in callalerting (i.e. in the forward direction, from the A-party equipment 1 tothe B-Party equipment 2) and in call acceptance (i.e. in the backwardsdirection, from the B-party equipment 2 to A-Party equipment 1).

The CCI identifier has the form of an at least 1 bit flag, suitable tobe fitted into existing protocols such as Session Initiation Protocols(SIP), Direct Transfer Application Part (DTAP), ISDN User Part (ISUP) orDigital Subscriber Signalling 1 (DSS1).

The CCI identifier survives, due to its format, transcription acrossvarious networks trough which it traverses. This is applicable when acall crosses a Gateway node between two networks, especially when thesetwo networks are heterogeneous, e.g. GSM & TDM or GSM & PSTN/ISDN.

The CCI identifier will also survive protocol translations, whereapplicable, e.g. if SIP-T gateways are used.

Resuming the generation, induction, detection and deletion of the CCIidentifier, the roles of the various entities in the traffic chain are:

-   Calling A-party, by means of the user equipment 1: the calling    A-party generates the CCI identifier and includes the CCI identifier    in the CS-call establishment towards the B-party's user equipment 2    or network service node 34; the calling A-party's user equipment 1    may also receive the CCI identifier from the network, by means of    the network based correlation node 5 or from the B-party's user    equipment 2/network service node 34.-   Network, implemented as network based correlation node 5: the    correlation node 5 receives the CCI identifier from the calling    A-party's user equipment 1, when it is included in the call    establishment towards the B-party's user equipment 2 or network    service node 34; the correlation node 5 may also receive the CCI    identifier from the called B-party's user equipment 2, when it is    included in the call acceptance from the B-party's user equipment 2    or network service node 34 towards the A-party's user equipment 1;    the correlation node 5 may also include, modify or delete the CCI    identifier in the call establishment towards the B-party's user    equipment 2 or network service node 34; and finally, the correlation    node 5 may include, modify or delete the CCI identifier in the call    acceptance from the B-party's user equipment 2 or network service    node 34 towards the A-party's user equipment 1.-   Called B-party, by means of user equipment 2 or network service node    34; the called B-party's user equipment 2 or network service node 34    receives the CCI identifier from the correlation node 5 or from the    A-party's user equipment 1; the called B-party's user equipment 2 or    network service

node 34 may also generate a CCI identifier and include it in the callacceptance towards the A-party's user terminal 1.

With reference to FIG. 1, the telecommunication network also comprises acharging subsystem 40 and an authentication subsystem 41. Bothsubsystems 40, 41 do have connections to two or more networks 11, 12, 13as to deploy their functionality according to prior art. Thesesubsystems may also be provided by a network node CCI in case of adetected correlation between the CS-call and the PS-session for acertain party.

FIG. 2 provides a survey of the elements of the user equipment 1.Interfaces 1A, 1B, 1C each associated with a network address, provideconnection to networks 11, 12, 13. A processor 102, comprising anapplication program storage 102A, and a memory unit 103, communicativelyconnected to the networks 11, 12 13 via Input Output interface 101, isarranged for setting up communication sessions, proving the networkaddress, accepting communication setup and receiving and storing the CCIidentifier

Correlation node 5 either receives the CCI identifier from the userequipment 1, the user equipment 2, the network service node 34, orprovides the CCI identifier, when the node 5 detects via the networkinterfaces 5A, 5B, 5C to networks 11, 12, 13 that the CS-call andPS-session of A-party's user equipment 1 is correlated in relationtowards the user equipment 1, 2, the network service node 34, thecharging subsystem 40 or the authentication subsystem 41.

With reference to FIG. 3, the correlation node 5 will be furtherexplained. The correlation node 5 is arranged to be queried by the userequipment 1 for verifying the presence of the first and secondcommunication session. The correlation node 5 comprises an I/O unit 501connected to networks 11, 12, 13 via network interfaces 5A, SB, 5C, aprocessing unit 502 with an application program storage 502A and amemory unit 503, and is arranged to determine correlation between thefirst and the second communication session.

By introduction of the method as provided, a simple and reliable methodis provided as to enable a correlation check. By introduction of the CCIidentifier, in cooperation with the existing CLI identifier, anindication is given that a CS-call and one or more PS-sessions arecorrelated. Hence a check should only be made in case the CCI identifieris set, thereby preventing execution of checks which were made in casesthat there was no correlation although a user equipment has more thanone communication session.

The invention as presented provides a solution to the problem aspresented at the background of the invention:

-   1) With a CS-call and the PS-session correlation enabled by the CCI    identifier it is possible to provide the user of a DTM phone 1 with    a rich alert, comprising e.g. a visual rendering. An IMS network    node may have generated the “rich” part of the call, provided in a    PS-session. In this case the alert at the receiving phone,    initialised by the CS-network, is now related to the visual    rendering at the receiving phone by having correlation between the    CS-call and the PS-session.-   2) With the CS-call and the PS-session correlation enabled by the    CCI identifier is possible to ease user interaction, where parties    involved in a CS-call are able to specify with ease (e.g. with a    single click of a button) that a picture, video or file shall be    sent to the party with which a speech communication is ongoing    (i.e., the current CS-call partner). In this case the ongoing    CS-call is correlated to the existing or new PS-session required for    sending said data portion.-   3) With the CS-call and the PS-session correlation enabled by the    CCI identifier, an ongoing combinational session enables charging of    the PS-session (e.g. exchange photos, share whiteboard, etc.)    between the A-party and the B-party with a different tariff than    normal, and present the user a single bill. In this case the    charging of the PS-sessions is correlated to the charging of the    CS-call as to present the said user a single bill, which is    traditionally related to CS-calls only.-   4) With the CS-call and the PS-session correlation enabled by the    CCI identifier, it is possible that during an ongoing CS-call to a    helpdesk or an assistance service, multimedia (pictures/video with    text) that illustrates the solution to the problem is sent. In this    case the ongoing CS-call is correlated to the PS-sessions where the    additional multimedia information is exchanged.-   5) With the CS-call and the PS-session correlation enabled by the    CCI identifier the QoS on the PS-session is influenced when the    CS-call is ongoing. Video streaming during the CS-call comprising a    voice call, can be handled with a higher priority. Here it is    required that the relation between the CS-call and the PS-session    has to be known by the user equipment, or in the network, or in    both, as to influence the QoS.-   6) With the CS-call and the PS-session correlation enabled by the    CCI identifier a network provider applies a policy to invoke the    same services to the second communication session as has been used    in the first communication session. If the first communication    session has been subject to the rules of a Virtual Private Network    (VPN), the second communication session can also be subject to the    rules of the same VPN, as the provider relies on the correlation of    both sessions.-   7) With the CS-call and the PS-session correlation enabled by the    CCI identifier, the receiving terminal 2 or network service node 34    may check and detect correlation and applies local policies to a    combinational session. E.g. a use always automatically accepts a new    session, which is started within the context of an ongoing session.    Such when the second communication session is accepted automatically    when the first communication session was already ongoing and the CCI    identifier was “set”.

What is claimed is:
 1. A method for providing correlation means within atelecommunications system comprising two or more networks of differentnetwork type, the two or more networks being connected to at least afirst user equipment and a network entity, where the first userequipment and the network entity have network connections, each networkconnection associated with a respective network address, to the two ormore networks, the method comprising the steps of: setting up a firstcommunication session by one of the first user equipment and the networkentity towards the other of the first user equipment and the networkentity, via the network of a first network type; setting up a secondcommunication session by one of the first user equipment and the networkentity towards the other of the first user equipment and the networkentity, via the network of a second network type, including providingthe network entity with a call session identifier being the networkaddress of the first network type of the first user equipment, the firstand second communication sessions being present on the two or morenetworks of different network type, the network types being a CircuitSwitched network type and a Packet Switched network type, and providinga correlation node, connected to the two or more networks, with aCombinational Call Indicator (CCI) variable, the CCI indicating whetherthe first communication session is combinational with the secondcommunication session, where the correlation node is adapted todetermine that the first and the second communication session arecombinational when the received CCI variable is set, wherein the settingup of the communication session that is present on the network of theCircuit Switched network type includes providing the CCI variable to theother of the first user equipment or the network entity towards whichthe communication session that is present on the network of the CircuitSwitched network type is set up.
 2. The method according to claim 1wherein the setting up step of the communication session that is presenton the network of the Packet Switched network type further comprises thestep of: providing the CCI variable to the other of the first userequipment or the network entity towards which the communication sessionthat is present on the network of the Packet Switched network type isset up.
 3. The method according to claim 1 wherein the setting up of thefirst communication session is performed before or after the setting upof the second communication session.
 4. The method according to claim 1wherein the setting up of the first communication session is performedsimultaneously with the setting up of the second communication session.5. The method according to claim 1 wherein the providing step of the CCIvariable is performed by the first user equipment.
 6. The methodaccording to claim 5 wherein the call session identifier is provided bythe first user equipment or the correlation node.
 7. The methodaccording to claim 1 wherein the providing step of the CCI variable isperformed by the network entity.
 8. The method according to claim 1wherein the first user equipment or the network entity sends a messageto the correlation node that the first communication session and thesecond communication session are regarded as combinational.
 9. Themethod according to claim 1 wherein the first user equipment or thenetwork entity verifies the established first or second communicationsession.
 10. The method according to claim 9 wherein the first userequipment or the network entity determines that the first and secondcommunication sessions are combinational when it is verified that thefirst or second communication session are established.
 11. The methodaccording to claim 1 wherein the network entity is a second userequipment or a network service node.
 12. The method according to claim11, wherein the first or the second user equipment comprises a userequipment of a type of terminal including a Dual Transfer Mode (DTM)terminal, a Global System for Mobile communications -General PacketRadio System (GSM-GPRS) user equipment or a Universal MobileTelecommunication System Multi Radio Access Bearer (UMTS Multi- RAB)terminal, with at least one connection to each connected network wheresaid at least one connection is associated with a network address. 13.The method according to claim 12 where the user equipment has either awire-line connection to the each connected network or a wirelessconnection to the each connected network.
 14. The method according toclaim 11 where the first or the second user equipment deploys acommunication session by means of a telephone, headset, Global Systemfor Mobile communications (GSM) terminal, Advanced Mobile Phone System(AMPS) or Digital AMPS (D-AMPS) terminal, Digital Enhanced CordlessTelephony (DECT) terminal, Bluetooth terminal, Universal MobileTelecommunication System (UMTS) terminal, video terminal, PersonalComputer (PC) or workstation.
 15. The method according to claim 11wherein a Calling Line Identification (CLI) comprises a network addressof one of the first user equipment, the second user equipment or thenetwork service node, the network address being of the first networktype.
 16. The method according to claim 15 wherein the CLI is includedin a header of a SIP Invite message.
 17. The method according to claim15 wherein the CLI is formatted as a SIP URI, to be comprised in a“From” header of a SIP Invite message.
 18. The method according to claim15 wherein an application at the one of the first user equipment, thesecond user equipment or the network service node generates and sendsthe CLI at setting up the first or second communication session.
 19. Themethod according to claim 1 wherein the two or more networks andassociated network addresses are of Circuit Switched (CS) type or PacketSwitched (PS) type.
 20. The method according to claim 19 wherein anetwork address of the CS type is a telephone subscriber number a PublicSwitched Telecommunications Network (PSTN) number, a Virtual PrivateNetwork (VPN) private number, or a number according to the E.164International Telecommunication Union (ITU) recommendation.
 21. Themethod according to claim 19 wherein a network address of the PS type isa PS network identifier or SIP Uniform Resource Identifier (URI) , anInternet Protocol (IP) address, or a Local Area Network (LAN) MediaAccess Control (MAC) layer address.
 22. A user equipment for operationin a telecommunication system, where the telecommunication systemcomprises two or more networks of different network type and where theuser equipment comprises: a plurality of network connections, eachnetwork connection being associated with a respective network address,to the two or more networks, and where the user equipment comprises anInput Output (I/O) unit communicatively connected to the two or morenetworks by means of the plurality of network connections, where the I/Ounit, in cooperation with a processing unit with an application programstored at a program storage and memory unit, is adapted for setting up afirst communication session and a second communication session onrespectively different ones of the two or more networks of differentnetwork type, for providing a network entity a call session identifierbeing a network address of the user equipment, for acceptingcommunication sessions, for receiving and storing the call sessionidentifier and for querying the network entity or a network node, thenetwork types being a Circuit Switched network type and a PacketSwitched network type; the user equipment being adapted to provide acorrelation node connected to the two or more networks with aCombinational Call Indicator (CCI) variable, for indicating that thefirst communication session might be combinational with the secondcommunication session; and wherein the setting up of the communicationsession that is present on the network of the Circuit Switched networktype includes providing the CCI variable to the network entity.
 23. Theuser equipment according to claim 22 wherein the user equipment isadapted for receiving the CCI variable and for providing the CCIvariable to the network entity.
 24. The user equipment according toclaim 22, wherein the I/O unit is further adapted for retrieving networkaddresses of the network entity via the two or more networks, andstoring the network addresses in the program storage and memory unit.25. The user equipment according to claim 22, wherein the processingunit with the application program stored at the program and storagememory unit is further adapted for querying the network entity or thecorrelation node in order to verify the presence of the firstcommunication session and the second communication session, the firstand second communication sessions being present on the two or morenetworks of different network type.
 26. The user equipment according toclaim 25, wherein the processing unit, loaded with the applicationprogram, is further adapted for determining a correlation between thefirst and the second communication session, and adapted for executingthe application program when the first and the second communicationsessions are determined to be combinational.
 27. The user equipmentaccording to claim 22, wherein the user equipment comprises a DualTransfer Mode (DTM) terminal, a Global System for Mobilecommunications - General Packet Radio System (GSM-GPRS) user equipmentor a Universal Mobile Telecommunication System Multi Radio Access Bearer(UMTS Multi-RAB) terminal.
 28. The user equipment according to claim 27where the user equipment deploys a communication session by means of atelephone, headset, Global System for Mobile communications (GSM)terminal, Advanced Mobile Phone System (AMFS) or Digital AMPS (D-AMPS)terminal, Digital Enhanced Cordless Telephony (DECT) terminal, Bluetoothterminal, Universal Mobile Telecommunication System (UMTS) terminal,video terminal, Personal Computer (PC) or workstation.
 29. The userequipment according to claim 27 where the user equipment has a wirelineconnection to the two or more networks or a wireless connection to thetwo or more networks.
 30. The user equipment according to claim 22,wherein the user equipment comprises two or more terminals where each ofthe terminals has at least one connection to each connected networkwhere each of said connections has a network address.
 31. The userequipment according to claim 22, wherein the two or more networks andthe associated network addresses are of either Circuit Switched (CS)type or Packet Switched (PS) type.
 32. The user equipment according toclaim 22, having a network address comprising: a CS type networkaddress, a Public Switched Telecommunications Network (PSTN) number, aVirtual Private Network (VPN) private number, or a number according to aE.164 International Telecommunication Union (ITU) recommendation. 33.The user equipment according to claim 22, having a network addresscomprising: a PS network identifier or SIP Uniform Resource Identifier(URI), an Internet Protocol (IP) address or a Local Area Network (LAN)Media Access Control (MAC) layer address.
 34. A correlation node foroperation in a telecommunication system, where the telecommunicationsystem comprises two or more networks of different network type, andwhere the correlation node has network connections, each networkconnection associated with a respective network address, to two or moreof the two or more networks, the correlation node comprising: an InputOutput (I/O) unit communicatively connected to the two or more networks,by means of the network connections, where the I/O unit in cooperationwith a processing unit utilizing an application program stored at aprogram storage and memory unit, the I/O unit being adapted forproviding a first user equipment or network entity with a call sessionidentifier, which is the network address of the first network typecorresponding to the first user equipment, and for receiving and storingthe call session identifier, the network types being a Circuit Switchednetwork type and a Packet Switched network type, the correlation nodebeing adapted to receive a Combinational Call Indicator (CCI) variable,for indicating whether a first communication session is combinationalwith a second communication session, and, during setup of acommunication session on the network of the Circuit Switched type, toprovide the CCI to the first user equipment or network entity towardwhich the communication session on the network of the Circuit Switchedtype is set up; where the correlation node is further adapted todetermine that the first and the second communication sessions arecombinational when the received CCI variable is set.
 35. The correlationnode according to claim 34 wherein the correlation node is furtheradapted for determining if the first and second communication sessionsbetween the first user equipment and the network entity arecombinational, the first and the second communication sessions beingpresent on the two or more networks of different network type.
 36. Thecorrelation node according to claim 34 wherein the correlation nodecomprises the Input Output (I/O) unit communicatively connected to thetwo or more networks, by means of interfaces, each interface having anetwork address, where the I/O unit is adapted for retrieving networkaddresses of the user equipment or the network entity via the two ormore networks, and storing said network addresses in the program storageand memory unit.